The Real Madrid forward began his message declaring that he been at the service of the national team "body and soul" despite the birth of the twins, adding: "Unfortunately we couldn't achieve our main sporting aim."

The semi-final in Kazan ended in a 0-0 draw and Chile went through as Ronaldo's teammates missed three penalties.

Little is known about the twins, although unconfirmed reports in Portugal said they were born on 8 June, well before the start of the Confederations Cup. The SIC TV channel said the boy and girl had been named Eva and Mateo.

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Media captionPeople cannot criticise my season - Ronaldo

Further reports said the Fifa footballer of the year's mother, Dolores Aveiro, travelled to the US soon after they were born.

In a statement, the Portuguese Football Federation (FPF) said it had been informed by Ronaldo before the Confederations Cup that he had become a father again, and yet had decided to travel to Russia with the team. The FPF described his decision as a "gesture that we must highlight and praise".

Instead of staying with the team for the third-place play-off on Sunday, Ronaldo was now going to leave the camp, it added. "We must release the athlete so he can finally get to know his children."

Ronaldo, who has a long-term girlfriend, model Georgina Rodríguez, left the team in Kazan on Thursday morning. There has been speculation in Portuguese media that she too is expecting a baby, after the footballer posted a picture on social media showing the couple sitting down with their hands on her stomach.

At the time the model appeared to reject the rumours, posting gym photos that suggested she was not pregnant, although it was unclear when the pictures were taken.

Image copyrightPA/Cristiano RonaldoImage caption
Last month, Cristiano Ronaldo released this photo on his Instagram feed with girlfriend Georgina Rodriguez